Significant Severe Weather Threat Friday, Esp Saturday!

Written by on October 12, 2012 in North and South America, United States of America with 0 Comments

With the pattern changing across North America with storms now pushing onto the West Coast and gone is the blocking high, we have a perfect setup coming up over the next couple of days for a severe weather outbreak. Friday starts things off out over Texas and Oklahoma where a dry line will slide east out of the southern Rockies, We are going to see start seeing fun and games kicking as we have a split jet over the West Coast with a big storm system rolling into the Four Corners aboard a vigorous sub tropical jet and of course we have a southbound northern branch jet which is drawing down the cold air out of Canada, it’s once that storm gets east of the Rockies where things converge and kick off in the form of strong to severe storms breaking out.

We have the perfect setup for a ‘2nd Severe Weather Season’ outbreak. Why is there a SECOND severe weather season? Well, very similar to spring, only it’s opposite as storms begin to intensify again and start tracking further south with jet streams tightening, there is cold air now over Canada which can get drawn south and with it still being October, there’s always plenty of residual heat and humidity down in the South and Gulf. All it takes is for a storm like we have right now, for some wild Plains weather as the system is what draws the warm/cold, dry/moist air together.

What the Calif storm system is going to do is, once it gets through the Four Corners, it will lift the southern branch jet north and in doing so it also draws heat and humidity north with it. At the same time, the circulation from the system also creates a trough in which the cold air to the north will get pulled south, this is the perfect setup Friday for an outbreak over the WESTERN High Plains of Texas and Okla but it’s Saturday where the two jet get close and all the heat and humidity gets lifted all the way up into where the cold air is coming out of the northwest. The clash zone and area with maximum lift will be over northern Arkansas, Missouri, Iowa, perhaps southern Illinois and modelling shows the jet maxes (front right rear entrance region) where there is enhanced upward motion, strong jet and what that’s doing by drawing a lot of heat and raising those dew points north out of the Gulf.

In the below 500 mb chart you can clearly see the Four corners storm system and the rather strong northwest jet dropping down over top.

The below chart shows the 300 mb vort maxes with the strong northern branch roaring the cold cold into the GL while a fairly strong southern branch is lifting north.

This is for Friday. What your looking for is, where the dark blues are on the southern branch, just on the front right, rear entrance region of that speed max is where your going to have your severe weather on Friday. This chart is 3-6 hours behind so that max should be over the TX-OK panhandles.

This is for Saturday. The bigger day.

Notice there’s some convergence but also pay attention to the fact the storm is lifting the southern brnach way north up into the northern branch and so the warmth and humidity is getting drawn right up into the where the cold is coming down. The region right where the two jet get closest or meet, is your prime region for severe storms.. More tomorrow!

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